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Impact of BMI on Ability to Successfully Create an IPAA

Khasawneh, Mohammad A., M.B.B.S.; McKenna, Nicholas P., M.D.; Abdelsattar, Zaid M., M.D., M.Sc.; Johnson, Angela, M.D.; Dozois, Eric J., M.D.; Pemberton, John H., M.D.; Mathis, Kellie L., M.D.

doi: 10.1097/DCR.0000000000000686
Original Contributions: Inflammatory Bowel Disease
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BACKGROUND: IPAA is the surgical treatment of choice for patients with ulcerative colitis. Limited data exist on how obesity impacts the ability of the surgeon to successfully create an IPAA.

OBJECTIVE: We aimed to determine how BMI affects the ability to successfully complete the operation.

DESIGN: This was a retrospective cohort study.

SETTINGS: The study was conducted at a single tertiary care center.

PATIENTS: We included all of the patients undergoing an IPAA for ulcerative colitis between January 2002 and August 2013 at our institution. A total of 1175 patients underwent proctocolectomy for ulcerative colitis during the study period; 129 were not offered IPAA (reasons included patient preference (n = 53), advanced age/comorbidity (n = 28), obesity (n = 23), incontinence (n = 8), suspicion of Crohn’s disease (n = 8), rectal cancer (n = 3), and other (n = 6)). Twenty-six patients had a concurrent cancer diagnosis, and 5 had a polyposis syndrome.

MAIN OUTCOME MEASURES: We used logistic regression modeling to estimate the association between BMI and unsuccessful pouch attempts.

RESULTS: Of the 1046 patients offered IPAA, 19 (1.82%) could not be technically completed at the time of surgery. Increasing BMI was associated with a higher risk of not being able to technically perform IPAA (OR = 1.26 (95% CI, 1.17–1.34)). The chance of an unsuccessful pouch rose from 2.0% at a BMI of 30 to 5.7% at a BMI of 35 and 15.0% at a BMI of 40 (p < 0.01). The area under the receiver operator characteristics curve was 0.82. BMI explained 21% of the variation in pouch success rate.

LIMITATIONS: This study is limited in its generalizability. Also, the verbosity within the operative dictations varied among surgeons, making it impossible to be certain which maneuvers were performed to gain length in each patient. In addition, we were limited to BMI as a surrogate for visceral obesity, and we did not include medical therapy at the time of IPAA attempt.

CONCLUSIONS: There is a strong association between increasing BMI and the ability to technically perform IPAA. Obese patients should be counseled to lose weight preoperatively to increase the probability of successful IPAA construction at the time of operation.

Division of Colon and Rectal Surgery, Department of Surgery, Mayo Clinic, Rochester, Minnesota

Financial Disclosure: None reported.

Podium presentation at the meeting of The American Society of Colon and Rectal Surgeons, Los Angeles, CA, April 30 to May 4, 2016.

Correspondence: Kellie L. Mathis, M.D., Division of Colon and Rectal Surgery, Mayo Clinic, Gonda 9S, 200 First Street SW, Rochester, MN 55905. E-mail: mathis.kellie@mayo.edu

Restorative proctocolectomy with IPAA has become the surgical procedure of choice for patients with medically refractory ulcerative colitis (UC). The procedure is also offered to patients with UC who develop malignancy or have early neoplastic changes. Over time, the indications for IPAA were broadened to include patients with familial adenomatous polyposis and select patients with Crohn’s disease.1 After it was described by Parks and Nicholls in 1978, several reports have demonstrated the efficacy of IPAA in treating patients with UC.2–5 Patients undergoing proctocolectomy and IPAA have an improved quality of life compared with patients undergoing Brooke ileostomy or Koch ileostomy.6,7 Functional outcome and quality of life after IPAA are also comparable with the general population.8 However, the procedure cannot be offered to every patient. Patient age and technical difficulties are factors that have been associated with failure of IPAA formation.9

Short- and long-term outcomes of IPAA have been well documented in several reports. Recent research has demonstrated that excessive weight gain after pouch surgery is an independent predictor of pouch failure.10 There is a paucity of data in the literature regarding the success of IPAA in overweight and obese patients. In an effort to guide surgeons in their preoperative counseling for patients seeking IPAA, we aimed to determine the relationship between patient BMI and technical success of IPAA.

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PATIENTS AND METHODS

Approval from the Mayo Clinic Institutional Review Board was obtained to review all of the patients with UC who were undergoing proctocolectomy (open or laparoscopic) between January 2002 and August 2013. Patients with UC as the indication for surgery were included in the analysis. Patients were excluded from the analysis if they were <18 years of age, had a primary diagnosis other than UC (ie, familial adenomatous polyposis or Crohn’s disease), had no research authorization, or were not deemed candidates for IPAA based on preoperative evaluation attributed to factors such as age or fecal incontinence.

Patients were identified using a prospectively maintained database. The authors reviewed all of the operative reports and recorded the success or failure in constructing IPAA, as well as any specific reasons for abandonment of the planned procedure. Patient demographics, including age, sex, and BMI at the time of the operation, were obtained from the medical chart.

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Exposure Variable

BMI was the main exposure in this analysis and was recorded as a continuous variable by dividing the patient’s weight in kilograms by their height squared.

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Main Outcome Variable

The success or failure of constructing an IPAA was the main outcome in this study. This was obtained from reviewing all of the operative reports and recorded specific reasons for abandonment of the planned procedure.

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Statistical Analysis

We used logistic regression to estimate the association between BMI and an unsuccessful pouch attempt. The statistical model allows for the calculation of an adjusted marginal rate (or probability) of an unsuccessful pouch across the range of BMI values. We used robust SEs to account for patient clustering between surgeons. For simplicity, we used BMI increments of 5 kg/m2 to obtain point estimates and obtained pairwise comparisons from the regression model. The model was constructed a priori to include BMI as a continuous variable, age as a continuous variable, and sex as a categorical variable. Several interactions were tested; however, none contributed to the overall performance of the model or qualitatively changed the results. Thus, the simplest model was chosen as indicated above. Using the logistic regression formula, BMI was fixed for all of the patients, whereas all of the other variables were kept as observed and a calculated adjusted probability (phat) was calculated.

Data management and analyses were performed using STATA version 13.1 (Stata Corp, College Station, TX). All of the tests were 2 tailed, and α was set at 0.05.

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RESULTS

A total of 1175 patients underwent proctocolectomy for UC during the study period. Fifty-nine percent (n=689) were men with a median age of 41.6 years (interquartile range, 28.0–54.0 years). A total of 129 patients were not offered IPAA and underwent proctocolectomy with an intended end ileostomy. Reasons for not considering IPAA included patient preference (n = 53), advanced age/comorbidity (n = 28), obesity (n = 23), pre-existing fecal incontinence (n = 8), suspicion of Crohn’s disease (n = 8), low rectal cancer (n = 3), and other (n = 6). Therefore, IPAA was planned in 1046 patients. Twenty-six patients had a concurrent diagnosis of malignancy, and 5 had a concurrent nonfamilial adenomatous polyposis syndrome.

Of the 1046 offered IPAA, 19 (1.82%) could not be technically accomplished at the time of surgery. The sole reason for failure of IPAA formation was inability to stretch the pouch/terminal ileum to the deep pelvis despite multiple maneuvers to lengthen the mesentery. In 258 patients (24.6%), specific technical intraoperative measures to lengthen the mesentery were described by the operating surgeon. Measures taken to achieve adequate length included mobilizing the terminal ileal and small-bowel mesentery up to the level of duodenum, dividing the peritoneum on both dorsal and ventral sides of the pouch mesentery, high ligation of the ileocolic pedicle, additional duodenal mobilization, and occasionally ligation of terminal pouch vessels. In 252 cases, the IPAA was performed in a 3-stage fashion; there was no correlation between stage of operation (first of 2 stages versus second of 3 stages) and IPAA success.

BMI was associated with unsuccessful pouch construction (p < 0.001). Age and sex were not predictive (Table 1). Increasing BMI was associated with a greater risk of not being able to technically perform IPAA (OR = 1.26 (95% CI, 1.17–1.34); p < 0.001; Table 2). For example, the chance of an unsuccessful pouch rose from 2.0% at a BMI of 30 to 5.7% at a BMI of 35 and 15.0% at a BMI of 40 (p < 0.001 between BMI 30 and 35; p = 0.004 between BMI 30 and 40; and p = 0.007 between BMI 35 and 40; Fig. 1). The area under the receiver operator characteristics curve, the C-statistic, was 0.82. BMI explained 21% of the variation in pouch success rate (pseudo-R2 = 0.212).

TABLE 1

TABLE 1

TABLE 2

TABLE 2

FIGURE 1

FIGURE 1

Of the 19 patients who did not have a pouch constructed, proctectomy with end ileostomy was performed in 12. In 4 patients, the rectum was left in situ (difficulty reaching the pouch was determined before completion proctectomy), and at least 3 patients were advised to lose weight before additional attempts at pouch creation. In the remaining 3 patients, an ileorectostomy was performed. One patient returned 34 months after the original IPAA attempt having lost 22 kg (BMI change from 39.6 to 29.8); he underwent successful proctectomy and IPAA. No other patients have undergone pouch construction at our institution to date.

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Post Hoc Analysis

We also sought to determine the relationship of height on the success of a pouch independent of weight or BMI. We ran the same model, substituting height as a quadratic variable for BMI. As shown in Figure 2, height does not substantially alter the probability of a successful pouch, although patients at both ends of the spectrum trended toward having an unsuccessful pouch.

FIGURE 2

FIGURE 2

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DISCUSSION

In this review, we evaluated the association between BMI and the ability to construct an IPAA in patients with UC. There was a strong and significant correlation between elevated BMI and inability to construct an IPAA. The main reason described by the surgeon for abandonment of IPAA was inadequate mesenteric length, and this was usually attributed to intra-abdominal obesity. To our knowledge, this is the first study describing the technical challenge of performing IPAA after proctocolectomy in obese patients.

The epidemic of obesity in the United States continues to be a major healthcare problem. The prevalence of obesity among US adults is estimated to be 36.5%.11 Seminerio et al12 recently evaluated the impact of obesity on the clinical course of patients with IBD. Interestingly, 71.9% of patients were above their ideal body weight, and 31.5% were obese. Obesity is more common in patients with UC compared with patients with Crohn’s disease.12 This finding is also supported by a recent review of 581 patients with IBD. The prevalence of obesity in patients with UC was similar to the general population.13

Browning and Nivatvongs9 reviewed 1789 consecutive IPAA attempts for patients with UC and familial adenomatous polyposis. The abandonment rate was 4.1%, and technical reasons accounted for the overwhelming majority of cases. Older patients (>40 years) were found to be at increased risk for abandonment. The authors explained their findings by increased incidence of obesity in older patients.9 In this review, age was not associated with failure to construct a pouch. Obesity, however, was found to be an independent risk factor for inability to achieve adequate length for the pouch to reach the deep pelvis without tension. The abandonment rate in our series was 1.8%, and obesity was commonly cited as the cause.

IPAA is usually performed as an elective procedure. Obesity increases the complexity of the operation and poses a challenge to the surgeon. Tension-free anastomosis is a key factor for success of the operation and long-term functional outcomes. Anastomotic leak or pouch ischemia resulting in pelvic sepsis can be life threatening. Several maneuvers have been described to achieve extra length for the mesentery to reach the deep pelvis without tension.14–17 Chu et al18 have proposed an intraoperative algorithm to achieve required length of the ileal pouch for a tension-free anastomosis with the anal canal. After complete mobilization of the small bowel, if the apex of the pouch reaches 3 to 4 cm below the inferior border of pubis, this is considered adequate. If not, other measures must be considered, including high ligation of the ileocolic artery or ligation of the distal superior mesenteric artery. Mesenteric lengthening can also be achieved by preserving the right colon marginal artery and the right branch of the middle colic artery with subsequent division of the right colic, ileocolic, and distal superior mesenteric arteries. The authors believe that >10 cm of length can be gained from this maneuver,18 but this is only possible if considered before the colectomy.

There are several limitations to our study. First, this is a single-institution retrospective review with a high degree of referred patients. Second, the verbosity within the operative dictations is highly variable among surgeons, making it impossible to be certain which maneuvers were performed to gain length in each patient. Third, we used BMI as a surrogate for visceral obesity because of the consistent reporting of BMI within the medical chart; we do not have other measures of visceral obesity, such as renal fat pad measurements on CT/MRI or waist circumference. Fourth, we did not include any medical therapy at the time of IPAA attempt, so that variable could not be accounted for in this study. Finally, the data presented represent a cumulative experience with an operation performed more than 3500 times by Mayo surgeons. It is, therefore, an experience that is generalizable, but only across surgeons with much exposure to patients needing total proctocolectomy for chronic ulcerative colitis. The occasional operator unfamiliar with the variables presented by complex patients with chronic ulcerative colitis needing operative intervention will likely find these outcomes not applicable to his or her practice.

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CONCLUSION

Obesity is prevalent among patients undergoing proctocolectomy and IPAA, and increasing BMI is associated with an inability to construct a pouch. Overweight and obese patients should be counseled about the risk of IPAA abandonment, and they should be encouraged to lose weight preoperatively when possible. When weight loss is not possible before colectomy, consideration should be given to a 3-stage procedure, with the IPAA creation delayed until adequate weight loss is achieved. Future studies in this regard should include prospective measures of visceral obesity.

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REFERENCES

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Keywords:

BMI; IPAA; Obesity; Outcomes; Ulcerative colitis

© 2016 The American Society of Colon and Rectal Surgeons